From the FDA Drug Label
Although failure of patients to show clinical improvement may reflect underdosage, it can also be indicative of overdosage. As is true of all cholinergic drugs, overdosage of pyridostigmine bromide may result in cholinergic crisis, a state characterized by increasing muscle weakness which, through involvement of the muscles of respiration, may lead to death Myasthenic crisis due to an increase in the severity of the disease is also accompanied by extreme muscle weakness, and thus may be difficult to distinguish from cholinergic crisis on a symptomatic basis The FDA drug label does not answer the question.
From the Research
Yes, myasthenia gravis that is not treated with medication can worsen respiratory status. Myasthenia gravis is an autoimmune disorder that affects the neuromuscular junction, causing muscle weakness that typically worsens with activity and improves with rest. When left untreated, the disease can progress to involve the respiratory muscles, including the diaphragm and intercostal muscles, leading to respiratory insufficiency or myasthenic crisis, which is a medical emergency. According to a recent study 1, continuous intravenous infusion of pyridostigmine or neostigmine can be a substitute for intravenous immunoglobulin or plasmapheresis if these are not available during crisis. However, caution should be observed because of possible complications such as cardiac arrhythmia and pneumonia.
Key Points to Consider
- Myasthenia gravis can progress to involve the respiratory muscles, leading to respiratory insufficiency or myasthenic crisis if left untreated.
- Common medications used to treat myasthenia gravis include acetylcholinesterase inhibitors like pyridostigmine and immunosuppressants such as prednisone, azathioprine, or mycophenolate mofetil.
- Patients with untreated myasthenia should be monitored closely for signs of respiratory compromise, including shortness of breath, difficulty completing sentences, shallow breathing, and decreased oxygen saturation.
- The respiratory decline occurs because antibodies block acetylcholine receptors at the neuromuscular junction, preventing proper muscle contraction necessary for breathing, as discussed in a study on the history of acetylcholinesterase inhibitors in the treatment of myasthenia gravis 2.
Treatment and Management
- Treatment should target the inciting event and airway support, as recommended in a study on myasthenia gravis and crisis evaluation and management in the emergency department 3.
- All acetylcholinesterase inhibitors should be avoided in crisis, including edrophonium testing and corticosteroids initially.
- Respiratory support can begin with noninvasive positive-pressure ventilation, as this has been successful even in patients with bulbar weakness.
- If intubation is necessary, consider avoiding paralytics or use a reduced dose of nondepolarizing agents, as suggested in a study on current and emerging treatments for the management of myasthenia gravis 4.